In recent years, it is widely conducted to obtain various information by measuring plural kinds of fluorescent substances for a reaction in a solution containing biological substances such as DNA, protein, lipid, and sugar labeled with plural kinds of fluorescent substances. One exemplary case includes labeling various DNA fragments having unknown nucleotide sequences with plural kinds of fluorescence, and measuring a binding state with a DNA fragment having a known nucleotide sequence that is solid-phased to a DNA chip or the like and complementarily binding thereto. Another example is application to a real-time PCR or the like that monitors nucleic acid (DNA) amplified by PCR in real time by utilizing a fluorescent substance.
The real-time PCR is advantageous in that amplification can be measured even in the course of temperature cycle and a quantitative result is obtained, and by detecting and analyzing a course of generation of an amplified product labeled with a fluorescent substance in PCR in real time, it is possible to conduct quantification more accurately. As a typical method conducted by using a fluorescent reagent containing a fluorescent substance, an intercalation method, a hybridization method and a LUX method are recited.
The “intercalation method” is a method of measuring a DNA amount utilizing the nature of a fluorescent substance such as SYBR (trademark) GREEN I, or ethidium bromide of breaking into double-stranded DNA during an elongation reaction, and generating fluorescence in response to emission of excitation light. The “hybridization method” is a method of detecting only a target PCR product using a DNA probe labeled with a fluorescent substance in addition to a PCR primer. In other words, by hybridization of a DNA probe labeled with fluorescence, with a target PCR product, the hybridized DNA (amount) is detected. The “LUX method” utilizes the property that a fluorescent signal of a fluorescent substance labeling oligo nucleic acid is influenced by the form (sequence, single strand or double strand, and so on) of the oligo nucleic acid. In an actual real time PCR, real time PCR is executed using a PCR primer labeled with one kind of fluorescent substance (LUX primer) and an unlabeled PCR corresponding to the same. The LUX primer is labeled with a fluorescent substance near 3′ terminal, and is designed to assume a hairpin structure with 5′ terminal. When the LUX primer assumes a hairpin structure, the quenching effect is canceled and the fluorescent signal increases. By measuring the signal increase, an amount of the PCR product can be measured.
For making such accurate quantitative measurement possible, more accurate and rapid optical measurement is required, and various devices have been developed for that. An optical fiber bundle is provided for each well, and part of optical fibers of the optical fiber bundle are used for emission of excitation light, and the remaining optical fibers are used for guiding fluorescence to a light receiving part. It is also proposed to provide the optical fiber bundle to be sequentially movable for each well (Patent Literature 1).